Maybe he'd like to get to know you better, but he's shy and unsure what to say in an actual message. Or, he might be the kind of guy who winks at a lot of woman and can't be bothered sending a message. If this is the case, it doesn't mean much.
The law of conservation of mass (from Lavoisier) states that mass can be neither created nor destroyed (but it may change its form into something that is not desired, such as heat with an engine) or that in a chemical reaction, the total mass of the reacting substances is equal to the total mass of products formed.
Dalton based his theory on two laws: the law of conservation of mass and the law of constant composition. The law of conservation of mass says that matter is not created or destroyed in a closed system. That means if we have a chemical reaction, the amount of each element must be the same in the starting materials and the products. We use the law of conservation of mass every time we balance equations!